The present invention relates generally to a coating apparatus used for producing two-tone patterns and more particularly to spray apparatus for applying a sharp-edged layer of coating.
When spraying is used to produce a sharp-edged film of coating in overlap over the surfaces, which may already be painted in a different color, of automobile bodies for example, so as to decorate them in two-tone design, it is considerably difficult to make sharply demarcated that edge of the film which is bounded on the adjacent differently colored area because portions of the sprayed paint particles flying across the boundary line to settle in the adjacent area. Various techniques have been used conventionally to obviate this problem. One method is to apply masking tape of suitable width along the dividing line on the side of the adjacent area that should not be sprayed. Another is to completely cover the adjacent area, exposing alone the surface to be sprayed. In either of these methods, desired effects have been obtained in preventing the masked area from being smeared with flying sprayed particles. However, these prior art methods have been found to pose problems. First, processes involved are in themselves not very efficient in actual practice and also not suitable for applications of conveyor-type line production. Second, the subsequent removal of the masking tape tends to cause the jagging of that edge of the film of coating which borders on the tape, since the removal is to destroy the coating of sprayed paint dried in a single layer across the surface of the tape. In other instances, this removal can entail the scraping of flakes off the layer along the edge of the film where the paint is not fully dried, together with the tape.